In recent years, use of a transparent plastic film as an electrode substrate instead of a glass sheet has been studied for displays (e.g., liquid crystal display and electroluminescence (EL) display) in order to implement a reduction in thickness, a reduction in weight, an improvement in flexibility, and the like.
A transparent plastic film used for these applications is normally required to have heat resistance and small in-plane retardation.
A melt extrusion method and a solution casting method have been known as a method for producing an optical film. In particular, the solution casting method has been considered to be a promising method for producing an optical film since the solution casting method can produce a flat and smooth film having small in-plane retardation.
When producing a film by the solution casting method using a resin having a high glass transition temperature, the solvent may volatilize to only a small extent, and the resulting film may include a large amount of residual solvent, and tends to curl.
Patent Document 1 discloses a method that produces a polyethersulfone film that includes a small amount of residual solvent using a solution casting method that utilizes a solution composition in which an aromatic polyethersulfone is dissolved in a solvent that includes 1,3-dioxolane.
However, since the drying step is performed while continuously increasing the heating temperature (see the examples of Patent Document 1), the drying step takes time, and productivity decreases.
Patent Document 2 discloses a resin composition that includes an amorphous thermoplastic resin (e.g., polycarbonate or polyethersulfone) and a bis(meth)acrylate that can be cured by applying active energy rays as a resin composition that may be used as an alternative to glass, and exhibits good chemical resistance and heat resistance. A member obtained using the resin composition is described in the examples of Patent Document 2. However, the member has a thickness as large as 1 mm. Patent Document 2 discloses a thermoplastic resin that includes an aromatic ring (e.g., polycarbonate and polyethersulfone) as the amorphous thermoplastic resin. However, Patent Document 2 does not provide production examples of a resin composition including a thermoplastic resin that includes an aromatic ring, and a member that utilizes such a resin composition.